Listed below are some of the possible causes of leaks:· Corrosion of tubes (“formicary corrosion”) increasing due to “tighter” house construction. Corrosion causes pinholes in the copper tubes· Corrosive gasses or fumes from defective drywall or other building materials, contents, or household chemicals.· AC coils being made of thinner-walled, lighter gauge copper· Higher operating pressures in newer equipment· Manufacturing defects in tubing